Saturday, July 14, 2012

Friday July 13th

We started off the day with an excellent minke whale. Minke whales are the smallest baleen whales we seen commonly in the Gulf of Maine and they tend to be quite erratic at the surface. This can make them difficult to whale watch. The individual we found, however, gave us some great views, as you can see below.

If you look closely in the first couple of images you can see a little like patch beside the whale. This is the pectoral fin of the whale. In Minke whales, the pectoral fin has a white patch on it, which is sometimes called a "Minke mitten", or more technically, an epaulet. These patches are white, but because of all of the green algae in the water, they appear green when viewed through the surface from the boat. You can just seen a green tinge in the photo, but the effect in more pronounced in person.

In this animation, you can see the full surfacing pattern of this Minke Whale. Notice how the snout comes up to the surface poking out first. For this reason these whales have sometimes been called "the little piked whales."

Later in the day we saw several fin whales, one of which we were able to identify as 9709. 9709 was first seen by the Blue Ocean Society on Jeffreys Ledge in 1997 (hence the 97 in its 'name'). We know this whale to be an adult female because she brought a calf to the ledge in 2007.

This is 9709 going on a deeper dive. Even without anything for scale, you can see this is a larger whale than the minke, since there is a great distance between the blow holes (still beneath the surface) and the dorsal fin. Fin whales can be 60-70 feet, while a very large Minke whale is only about 30 feet.

Our last sighting of the day was of Ebony, an adult female humpback whale. Ebony got her name from her jet black tail. This is a name with a long history; the word ebony actually comes to English from Ancient Egyptian (by way of Latin and Greek). Millennia ago, the Ancient Egyptians used the word to describe dark dense wood just as we do today.

Ebony the whale also has a long history, she was first sighted in 1980 or 1981. We know she is a female since she has brought at least 10 calves to the Gulf of Maine. The first of these calves was born in 1983, while the latest was born in 2007. For 24 years, Ebony has been a reproductively active whale. Humpback whales become mature somewhere around 8 years old, so a minimum age for Ebony might be around 37. This whale was showing no signs of senility as we were watching her as she engaged in some active behavior breaching and flipper slapping at the surface as we were approaching her.

It isn't well known how long humpback whales can live, or for how long females can produce calves, but by keeping track of whales like Ebony who can be re-sighted and identified by the natural markings on their body and tail, researchers in the Gulf of Maine can begin to get a handle on the life history of these animals.

Here is the underside of Ebony's tail. This is the main feature used to identify humpback whales and generally includes a pattern of both black and white. Ebony has only black of her tail. In the case of Ebony we have to use other features to determine that it is her, such as the shape of her dorsal fin (not pictured), or the shape of the trailing edge of her tail, which has crags and bumps you can just make out in this picture.

Ebony going down for a deeper dive, this is the top or dorsal side of her tail, right before she flips it up and disappears under the surface.

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